Freshwater flux in oceanic atolls

Team members: Mayukh Dey, Rohan Arthur, Jagdish Krishnaswamy, and Chris Perry

Groundwater within coral atolls is a finite resource that is dependent largely on the amount of rainfall that percolates through the soil. Since freshwater is less dense than saline seawater, all percolating groundwater floats as a thin lens on top of the denser seawater. Depending on the height of the soil above, groundwater can easily be found at depths of 2-5 m below ground. 

Atolls freshwater is also threatened by potential contamination by saline incursions through storms and strong waves, underscoring the connection between the buffering property of healthy reefs and freshwater availability. Saltwater contamination can render groundwater non-potable for months until the saline water is flushed out. With climate change, the frequency of intense storms and the likelihood of overwash and saline incursion are expected to increase.

While factors that lead to the accumulation of groundwater are well known in the literature, we do not yet have a good estimate on the availability of groundwater across all atolls and how this changes based on erratic rainfall, constant water demands by people, and transpiration related loss by coconut trees.

Groundwater loss in the Lakshadweep mainly occurs through local extraction for daily consumption and evapotranspiration by island vegetation. It is, therefore, crucial to understand how extraction pressures and variable climate and rainfall patterns stress these finite groundwater lenses.

Project objective: 

To estimate how total freshwater availability in the islands of Kavaratti, Agatti, and Kadmat have fluctuated since the year 2012. 

Using monthly rainfall data, we estimate the total volume that is available for extraction and how extraction rates often compound and create water-stress conditions in certain times of the year. To document how much water is being lost on a daily basis, we use data collected from observation wells and soil moisture sensors to estimate fluctuations in groundwater levels. We hope that our inquiry will shed light on the intricate relationship between rainfall patterns, and extraction rate, and how water conservation can be designed based on island-specific conditions.

Team members: Mayukh Dey, Rajeswari Bhai BT and Rohan Arthur

Rainfall is the only form of groundwater recharge and many societies living in atolls often live with these biogeophysical limitations in mind. It is therefore important to quantify the amount of water that atoll communities consume to better design and inform policy around freshwater conservation in atolls.

Our study explores the social dimensions of freshwater consumption in the atolls of Lakshadweep. After estimating the current levels of freshwater consumption in Kavaratti, Agatti, and Kadmat. We look at history to understand what practices had evolved in the region and how. Many such regional methods of water conservation have eroded in the community. We then explore how the state and social institutions are dampening or accentuating this change. We then look to the future and comment on what these patterns of freshwater consumption and conservation mean for the islands and what can be done to add resilience to this critical habitability pillar in the future.